I honestly love Valen. I had a friend several years ago who had a son named Valen, I remember thinking it was one cool name! I also like Vale/Vail for a boy, though, too. I can't really see Valen on a girl because of her son, but strangely enough, I sort of like Valens for a girl. Or you could do something like Valentina, which marks it firmly in the feminine camp, and use the nn Valen/Valens?

The name makes me think of two people: Roman Emperor Valens and singer Richie Valens who sang the 50's song "La Bamba" and died in a plane crash with BuddyHolly. I can only see the name on a boy. It does remind me of drapery word "valance" so I don't have a great liking for the name.